A well known structure of light-emitting diodes includes a growth substrate, n-type semiconductor layer, p-type semiconductor layer, and a light-emitting layer between the two semiconductor layers. A reflector for reflecting light from the light-emitting layer is also optionally formed in the structure. In some cases, to improve at least one of optical, electrical, and mechanical characteristics of the light-emitting diode, a well-selected material is used to replace the growth substrate and as a carrier to support the remaining structure without the growth substrate. For example, metal or silicon is used to replace sapphire substrate on which nitride is grown. The growth substrate is removed by etching, lapping, laser removal, etc. In addition, a transparent oxide can be adopted into the light-emitting diode to improve the current spreading.
There are several approaches to form an ohmic contact between the replacing carrier and the growth substrate. One of related materials can be referred to E. Fred Schubert, “Light-Emitting Diodes” chapter 9 (2006). Furthermore, the light-emitting diode finished products are made after being diced from a wafer; therefore, a suitable means used to protect semiconductor layers during the dicing process also becomes a notable issue. A usual protection means is a passivation layer formed on side walls of the semiconductor layer before dicing, but a careful control must be carried in each relevant step to avoid negative impact of forming the passivation layer.